Postsaccadic target blanking prevents saccadic suppression of image displacement

Abstract

Displacement of a visual target during a saccadic eye movement is normally detected only at a high threshold, implying that high-quality information about target position is not stored in the nervous system across the saccade. We show that blanking the target for 50-300 msec after a saccade restores sensitivity to the displacement. With blanking, subjects reliably detect displacements as small as 0.33 deg across 6 deg eye movements, with correspondingly steep psychophysical functions. Performance with blanking in a fixation control is inferior, evidence for a saccadic enhancement of sensitivity to image displacement. If blanking is delayed so that the target is visible immediately after the saccade in its displaced position, performance declines to non-blanking levels. Blanking the target before the saccade, and restoring it during the saccade, yields a similar but weaker effect. We interpret these results with a model in which the visual system searches for the postsaccadic goal target within a restricted spatiotemporal window. If it is not found, the assumption of stationarity of the world is broken and the system makes use of other information such as extraretinal signals for calibrating location.